1. Field of the Invention
The present invention relates generally to medical testing devices for determining mechanical load specifications of a medical implant specimen. More particularly, exemplary embodiments of the present invention relate to a medical testing device that allows multiple mechanical load specifications to be determined using a single device.
2. Description of the Related Art
The mechanical/physical testing of materials by taking a test specimen and applying tension and/or compressive force loads using an actuator is well known in the art. Typically, when testing a specimen, a single actuator is used which, if properly controlled, can apply a single time varying uniaxial force. However, force loading upon a specimen is rarely from a single source at a single frequency, also known as a static test. In other cases, there may be multiple load sources, each of which apply time varying loads of different frequencies, that is, dynamic testing. Accordingly, testing machines have been developed to apply multiple uniaxial force loads simultaneously. One such testing machine is disclosed, for example, in U.S. Pat. No. 5,425,276.
In addition to uniaxial testing of materials or test specimens, there also exist devices to apply simultaneous multiple mechanical loads, forces and/or moments, in a plurality of degrees of freedom. In this manner, the testing device can more accurately simulate real life forces and moments applied to a test specimen. For example, in order to properly perform a dynamic characterization of an artificial knee joint, it is necessary to replicate or simulate as accurately as possible all forces and moments applied to the artificial knee joint when it is surgically implanted into an individual. This would include simulating static forces on the artificial knee joint from the weight of the individual, simulating forces and moments applied to the artificial knee joint as the individual walks and runs.
In addition there are testing devices having a multiple degree of freedom arrangement as in, for example, U.S. Pat. No. 6,058,784. In such devices, a test specimen is loaded within the testing device where the testing device is loaded with multiple actuators in different directions acting upon the test specimen simultaneously.
The above devices are problematic; however, in several regards. First, the devices having a single actuator requires the purchase, maintenance, and use of multiple devices to properly test different testing upon a single specimen. The devices having multiple actuators acting upon the single specimen simultaneously are expensive to purchase, maintain, and use. In addition, a particular failure of a device may not be as readily pinpointed with so many forces being applied simultaneously.
Thus, what is desired is an economical device for testing multiple types of mechanical loads upon a single test specimen.